BH250-30
Title
BH250-30
Subject
Kyanite Schist
Description
Major Mineral: kyanite
Mineralogy Comments: small-size kyanite crystals
Texture: perfect kyanite cleavage
BH250-30 and BH250-30b – Kyanite Schist
These samples are kyanite-bearing schists, composed predominantly of medium- to coarse-grained kyanite within a foliated matrix of quartz, mica, and other accessory minerals. Kyanite, an aluminosilicate polymorph with the formula Al₂SiO₅, is a key metamorphic index mineral. Its stability field indicates formation under high-pressure, relatively low-temperature conditions, typically within the blueschist to amphibolite facies.
The presence of abundant kyanite points to a pelitic protolith—metamorphosed aluminum-rich sedimentary rocks such as shale, mudstone, or siltstone. During regional metamorphism, these fine-grained sediments recrystallized under directed pressure, producing the pronounced schistosity and alignment of micas seen in the samples.
Kyanite schists often form in convergent margin settings or continental collision zones, where rocks are subducted or deeply buried. The mineral assemblage in BH250-30 and BH250-30b thus records not only the composition of the original sediment but also the tectonic environment and pressure–temperature trajectory of metamorphism.
Mineralogy Comments: small-size kyanite crystals
Texture: perfect kyanite cleavage
BH250-30 and BH250-30b – Kyanite Schist
These samples are kyanite-bearing schists, composed predominantly of medium- to coarse-grained kyanite within a foliated matrix of quartz, mica, and other accessory minerals. Kyanite, an aluminosilicate polymorph with the formula Al₂SiO₅, is a key metamorphic index mineral. Its stability field indicates formation under high-pressure, relatively low-temperature conditions, typically within the blueschist to amphibolite facies.
The presence of abundant kyanite points to a pelitic protolith—metamorphosed aluminum-rich sedimentary rocks such as shale, mudstone, or siltstone. During regional metamorphism, these fine-grained sediments recrystallized under directed pressure, producing the pronounced schistosity and alignment of micas seen in the samples.
Kyanite schists often form in convergent margin settings or continental collision zones, where rocks are subducted or deeply buried. The mineral assemblage in BH250-30 and BH250-30b thus records not only the composition of the original sediment but also the tectonic environment and pressure–temperature trajectory of metamorphism.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-30. Housed at Carleton College in Minnesota.
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-30,” BH250 Mineralogy Teaching Collection, accessed April 26, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/33.